Soft capsules, which contains gelatin produced from bone and skin of cows and pigs, as a main component, and which are produced by a rotary die system automatic soft capsule manufacturing machine, have conventionally been widely used in the fields of “medical products” and “so-called health foods”.
However, since occurrence of BSE (Bovine Spondiform Encepralopany) was recently reported, attention has been focused on development of soft-capsule shell using a non-animal derived material instead of using animal-derived gelatin.
In the circumstance, Patent Documents 1 and 2 disclose an encapsulation technique using a combination of carrageenan gum and mannan gum as a gelatinizer without using gelatin. Also, Patent Document 3 discloses an encapsulation technique using κ carrageenan. Furthermore, Patent Document 4 discloses a technique on capsules using τ carrageenan and κ carrageenan. Moreover, Non-Patent Document 3 discloses that λ carrageenan provides high viscosity but does not turn into a gel.
As the properties of τ carrageenan and κ carrageenan, Non-Patent Document 1 describes “when κ- or τ-carrageenan is dispersed in water and heated to about 60° C. or more, a carrageenan molecule is dissolved in the form of a random coil. The solution is continuously cooled to form a double helix. This serves as a junction zone and then gelatinization starts”. Due to such a property, when an encapsulation film is formed using τ carrageenan and κ carrageenan, the encapsulation film sheet must be heated at a temperature higher by about at least 20 to 30° C. than the temperature of the case where gelatin is used as an encapsulation film. Because of this, a large heat load is applied to a capsule filling. This causes a problem in quality and lowers the efficiency of heat energy.
Under the circumstances, the present inventors noticed that if an encapsulation film can be formed by using λ carrageenan (see Non-Patent Document 2 and Non-Patent Document 3) which does not turn to a gel unlike κ carrageenan and τ carrageenan, encapsulation can be made without applying heat load to a capsule filling just by applying the same level of temperature as in a conventional gelatin sheet (temperature of a segment section: usually 35 to 50° C.) to an encapsulation film sheet, and advantageously improves heat energy efficiency. Then, the present inventors conducted inventive studies by themselves and successfully developed a soft capsule having a non-animal derived shell portion (capsule shell) using starch, λ carrageenan, a metal salt, dextrin, plasticizer, and water, and filed a patent application (Japanese Patent Application No. 2007-082542) in advance. Note that, since the prior patent application “Japanese Patent Application No. 2007-082542” was not published at the time this patent application was filed, this was not conventional art.
However, in a method for manufacturing a soft capsule having a non-animal derived capsule shell using starch, λ carrageenan, a metal salt, dextrin, a plasticizer, and water by means of a conventional rotary die system automatic soft capsule manufacturing machine (for example, Patent Documents 5 and 6), since drying capacity in a step of manufacturing a non-animal derived capsule shell-sheet is insufficient, dry load must be reduced by reducing a moisture content of a capsule shell solution.
However, if the moisture content is reduced, it becomes difficult to remove air incorporated in the capsule shell solution in a defoaming step. Visible air foams remain in the capsule shell-sheet. In short, a capsule having a defoaming defect is formed. This is a problem.
Furthermore, even if a conventional rotary die system automatic soft capsule manufacturing machine is used and dry load is reduced by reducing a blending ratio of moisture content, it must take time to supply a highly viscose capsule shell solution. When a rate of filling a soft capsule is increased, neither drying capacity in the capsule shell-sheet manufacturing step nor supply of the capsule shell solution fails to follow, preventing improvement of productivity.    Patent Document 1: U.S. Pat. No. 5,342,626    Patent Document 2: Japanese Patent Laid-Open No. 6-329833    Patent Document 3: U.S. Pat. No. 6,214,376    Patent Document 4: National Publication of International Patent Application No. 2003-504326    Patent Document 5: Japanese Patent Publication No. 5-88143 (cooling drum)    Patent Document 6: Japanese Patent Laid-Open No. 2003-40768 (servo)    Non-Patent Document 1: “New development of natural biopolymer material” edited by Takeaki Miyamoto et al., CMC publishing Co., Ltd, popular edition first copy issued on Nov. 28, 2003, pages 64 to 65.    Non-Patent Document 2: Chuo Foods Material Co., Ltd., “Home Page of Chuo Foods Material Co., Ltd.”, [onlion], “contents of a corporation    (2002)“→”carrageenan“→”properties of carrageenan”→section of “gelatinization properties” [searched on Jan. 30, 2007], Internet <URL http://www.chuofoods.co.jp/jgc03.html>    Non-Patent Document 3: FMC biopolymer department, “outline of carrageenan” pages 6 to 7